The present invention relates to a dry imaging system wherein the sensitized medium is contained in a layer of capsules.
More particularly, the present invention relates to an imaging sheet provided on one surface with a layer of capsules having a radiation sensitive internal phase containing a decolorizing agent which is associated with a layer of a background dye; wherein images are formed by image-wise exposing the imaging sheet to actinic radiation and rupturing the capsules such that an exposure-controlled, image-patterned release of the decolorizing agent occurs, the decolorizing agent thereafter reacting, image-wise, with the dye layer to form images in the form of colored and uncolored or pale areas.
The present invention also relates to an imaging system in which the aforesaid imaging sheet is associated with a dye precursor and a dye developer in which the decolorizing agent is released as above and reverses or inhibits the color-forming reaction.
Imaging systems based on encapsulated photosensitive systems are known.
Berman, U.S. Pat. No. 3,219,446 discloses a transfer imaging process in which an azo-blue "B" black dye is encapsulated with a cross-linkable polymer or a polymerizable monomer as fluid-droplets dispersed in a binder layer or fluid droplets contained in a layer of microcapsules. As described, imaging is accomplished by image-wise exposing a layer of the encapsulated dye to electromagnetic radiation. In the exposed areas the encapsulated fluid droplets are hardened by exposure and the dye cannot transfer to a copy sheet. In the unexposed areas, the fluid droplets remain fluid and the dye is transferred to the copy sheet in the form of an image.
Phillips, U.S. Pat. No. 3,700,439 discloses a photocopy process wherein Michler's ketone is encapsulated in a conventional manner and provided as a layer on a support. Michler's ketone itself is not a color former, but patterned irradiation of the ketone in the capsules produces a latent image of colorless, acid-colorable, dye precursor from the ketone. Images are developed by rupturing the capsules and contacting irradiated and non-irradiated ketone with an acid developer. Upon contact with the acid developer, the irradiated ketone produces a visible image. Phillips discloses both a system wherein the exposed imaging sheet is calendered face-to-face with an acid-coated receiving sheet to form images and a self-contained system wherein the acid developer is on the same surface as the capsule coating.
Berman et al, U.S. Pat. No. 3,072,481 discloses another type of encapsulated light sensitive element which utilizes a light-sensitive material which is readily converted to a colored form by irradiation when carried in a liquid vehicle but which is insensitive when solid. By encapsulating such a material with a volatile solvent, image-wise exposing a layer of the encapsulate, and rupturing the capsules to evaporate the solvent, an image is obtained in the exposed areas whereas the non-image areas are fixed by evaporation of the solvent.
Forris, U.S. Pat. No. 3,001,873, discloses a more complex system wherein the walls of capsules containing a solid dye are photosensitized such that patterned exposure renders the capsules unswellable. By wetting the sheet and heating, the unexposed capsules are swollen and rendered rupturable whereas the dye is immobilized in the exposed areas. Thereafter, by rupturing the swollen capsules in contact with a receiving sheet, image-wise transfer of the dye occurs from the unexposed areas only.